1. Field of the Invention
The invention concerns a tubular turbine generator unit as well as power station facility, including such a tubular turbine generator unit in a flow channel.
2. Description of the Related Art
Tubular turbines are usually installed in flow channels of retaining dams and exhibit a typically pear-shaped tubular turbine housing close to the turbine rotor disk. Thus the tubular turbine housing accommodates an electrical generator, which is driven by the turbine rotor disk via a drive shaft. Moreover the tubular turbine housing enables to guide the flow and hence improves the incoming flow into the turbine rotor disk. Accordingly, the major section of the tubular turbine housing is arranged upstream of the turbine rotor disk. A generic tubular turbine generator unit is illustrated in document CH 389 769.
In addition to large-sized tubular turbine generator units, compact embodiments are also known which can be applied for instance for smaller power plant facilities, such as river water power stations or replace large-sized tubular turbine generator units in the form of matrix-shaped multiple configurations.
Larger tubular turbine generator units usually present an inlet opening to the inside of the tubular turbine housing for inspection and maintenance purposes, wherein access is normally provided through a hollow pillar or a separate pit, which connects the side surface of the flow channel and the tubular turbine housing. Maintenance tasks for which such access to the inside of tubular turbine housing is necessary are in particular intended for the bearings, usually with oil lubrication. An alternative with water lubricated bearings is divulged in document JP 2002221141 A2. Moreover the electrical generator as well as the components of the power electronics create such a waste heat that an additional cooling system is necessary. The components of the cooling system require there again a regular service.
The cooling system assigned to a tubular turbine generator unit requires quite an expensive construction. Corresponding realisations are known, using heat exchangers external to the tubular turbine housing—see for example document JP 6042443 A2. External cooling systems for the bearing oil have moreover been known since documents JP 53.16691 A2 and U.S. Pat. No. 4,308,464A. Besides, cooling facilities accommodated inside the tubular turbine housing are divulged in documents WO 07147187 A1. JP 6237554 A2 and AT 403863 B. To do so, system with air cooling or a combination of air and liquid cooling are used. It may be referred by way of example to documents NL 87 583 C and FR 2 209 240 C.
To dispense with additional constructive measures for cooling purposes document EP 1318299 A1 suggested to locate the components of the electrical generator close to the side surface inside the tubular turbine-housing by using a permanently excited rotor which is exclusively cooled via heat circulation to the outer skin of the tubular turbine housing and heat extraction by the surrounding water brushing past. This sets however particular requirements to the configuration of the electrical generator as regards material selection and expected performance, which restricts construction options and increases the production costs of the electrical generator.
Another difficulty with known tubular turbine generator units consists in sealing the inside of the tubular turbine housing against the surrounding water. The shaft seal is an essential component to prevent any water inflow from penetrating the drive shaft through the tubular turbine housing. This component requires expensive construction, increases mechanical friction and may create a source of contamination for the driving surrounding water by causing total loss lubrication.
If surrounding water inflow inside the tubular turbine housing cannot be completely excluded, draining respectively bilge systems prove necessary. See for instance document JP 10159701 A2. Mostly, these system must be fitted with oil separators, in case the bearings of the drive shaft are provided with an oil lubrication system.